Li recovery processes and onsite chemical production for Li recovery processes

Abstract

In this disclosure, a process of recycling acid, base and the salt reagents required in the Li recovery process is introduced. A membrane electrolysis cell which incorporates an oxygen depolarized cathode is implemented to generate the required chemicals onsite. The system can utilize a portion of the salar brine or other lithium-containing brine or solid waste to generate hydrochloric or sulfuric acid, sodium hydroxide and carbonate salts. Simultaneous generation of acid and base allows for taking advantage of both chemicals during the conventional Li recovery from brines and mineral rocks. The desalinated water can also be used for the washing steps on the recovery process or returned into the evaporation ponds. The method also can be used for the direct conversion of lithium salts to the high value LiOH product. The method does not produce any solid effluent which makes it easy-to-adopt for use in existing industrial Li recovery plants.

What is claimed is: 
     
       1. A membrane electrolysis cell for processing a salt- containing solution, the membrane electrolysis cell comprising:
 an inlet through which the salt-containing solution is introduced into an interior of the membrane electrolysis cell; 
 an anode positioned to extend within the interior of the membrane electrolysis cell and positioned in an anode compartment; 
 a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode including a diffusion layer configured to diffuse a gas comprising O 2  and a hydrophilic catalyst layer disposed on a surface of the diffusion layer, the hydrophilic catalyst layer having a hydrophilicity greater than that of the diffusion layer and the hydrophilic catalyst layer being configured to transport negative ions; 
 a gas inlet through which the gas comprising O 2  is introduced into contact with the gas diffusion electrode; 
 a first ion exchange membrane interposed between the anode compartment and the hydrophilic catalyst layer of the gas diffusion electrode, the first ion exchange membrane being configured to exchange ions received from the anode to an opposed surface of the first ion exchange membrane; and 
 at least one outlet through which a product of the salt solution is removed from an interior of the membrane electrolysis cell. 
 
     
     
       2. The membrane electrolysis cell of  claim 1 , further comprising a second ion exchange membrane, the second ion exchange membrane being disposed on the hydrophilic catalyst layer of the gas diffusion electrode and being configured to exchange ions received from the hydrophilic catalyst layer of the gas diffusion electrode to an opposed surface of the third ion exchange membrane;
 wherein the first and second ion exchange membranes define a base build up compartment interposed between the cathode compartment and the anode compartment. 
 
     
     
       3. The membrane electrolysis cell of  claim 2 , further comprising
 a third ion exchange membrane, the third ion exchange membrane being interposed between the first ion exchange membrane and the anode compartment, wherein the first and third ion exchange membranes define a salt depletion compartment interposed between the anode compartment and the base build up compartment, the third ion exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposed surface of the third ion exchange membrane. 
 
     
     
       4. The membrane electrolysis cell of  claim 3 , further comprising:
 a fourth ion exchange membrane, the fourth ion exchange membrane being interposed between the third ion exchange membrane and the anode compartment, wherein the third and the fourth ion exchange membranes define an acid build up compartment interposed between the anode compartment and the salt depletion compartment, the fourth ion exchange membrane being configured to exchange ions received from the anode compartment to an opposed surface of the fourth ion exchange membrane and into the acid build up compartment. 
 
     
     
       5. The membrane electrolysis cell of  claim 4  wherein the first and fourth ion exchange membranes comprise cation exchange membranes and the second and third ion exchange membranes comprise anion exchange membranes. 
     
     
       6. The membrane electrolysis cell of  claim 4  wherein the hydrophilic catalyst layer comprises platinum and carbon and an anion exchange ionomer. 
     
     
       7. A membrane electrolysis cell for processing a salt-containing solution, the membrane electrolysis cell comprising:
 an anode positioned to extend within the interior of the membrane electrolysis cell and positioned in an anode compartment; 
 a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse a gas comprising O 2  and a catalyst layer disposed on a surface of the first diffusion layer, the catalyst layer having a hydrophilicity greater than that of the diffusion layer and the catalyst layer being configured to transport negative ions; 
 a base build up compartment and a salt depletion compartment interposed between the cathode compartment and the anode compartment, the base build up compartment is interposed between the cathode compartment and the salt depletion compartment, and the salt depletion compartment is interposed between the base build up compartment and the anode compartment; 
 a first anion exchange membrane, the first anion exchange membrane being disposed on the catalyst layer of the gas diffusion electrode and being configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposed surface of the first anion ion exchange membrane into the base build up compartment; 
 a cation exchange membrane interposed between the salt depletion compartment and the base build up compartment, the cation exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposed surface of the cation exchange membrane into the base build up compartment; 
 a second anion exchange membrane interposed between the salt depletion compartment and the anode compartment, the second anion exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposed surface of the second anion exchange membrane into the anode compartment; 
 an inlet through which the salt-containing solution is received into the salt depletion compartment; 
 a gas inlet positioned in the cathode compartment through which the gas comprising  02  is introduced into contact with the gas diffusion electrode; and 
 at least one outlet through which a product is removed from an interior of the membrane electrolysis cell. 
 
     
     
       8. The membrane electrolysis cell of  claim 7 , wherein the catalyst layer is hydrophobic or hydrophilic. 
     
     
       9. The membrane electrolysis cell of  claim 7 , wherein the catalyst layer comprises a first catalyst and an anion exchange ionomer. 
     
     
       10. The membrane electrolysis cell of  claim 9 , wherein the catalyst comprises a transition metal. 
     
     
       11. The membrane electrolysis cell of  claim 9 , wherein the catalyst comprises Pt. 
     
     
       12. The membrane electrolysis cell of  claim 9 , wherein the anion exchange ionomer comprises FumionT” ionomer or IonomrTM anion exchange ionomer. 
     
     
       13. The membrane electrolysis cell of  claim 7 , wherein the diffusion layer comprises carbon fiber paper, carbon felt, carbon cloth, or a porous metal structure. 
     
     
       14. A membrane electrolysis cell for processing a salt-containing solution, the membrane electrolysis cell comprising:
 an anode positioned to extend within the interior of the membrane electrolysis cell and positioned in an anode compartment; 
 a cathode comprising a gas diffusion electrode positioned to extend within the interior of the membrane electrolysis cell and positioned in a cathode compartment, the gas diffusion electrode comprising a diffusion layer configured to diffuse a gas comprising  02  and a catalyst layer disposed on a surface of the diffusion layer, the catalyst layer having a hydrophilicity greater than that of the diffusion layer and the catalyst layer being configured to transport negative ions; 
 a base build up compartment, a salt depletion compartment and an acid build up compartment interposed between the cathode compartment and the anode compartment, the base build up compartment is interposed between the cathode compartment and the salt depletion compartment, the salt depletion compartment is interposed between the base build up compartment and the acid build up compartment, and the acid build up compartment is interposed between the salt depletion compartment and the anode compartment; 
 a first anion exchange membrane, the first anion exchange membrane being disposed on the catalyst layer of the gas diffusion electrode and being configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposed surface of the first anion ion exchange membrane into the base build up compartment; 
 a first cation exchange membrane interposed between the salt depletion compartment and the base build up compartment, the cation exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposed surface of the cation exchange membrane into the base build up compartment; 
 a second anion exchange membrane interposed between the salt depletion compartment and the acid build up compartment, the second anion exchange membrane being configured to exchange ions received from the salt depletion compartment to an opposed surface of the second anion exchange membrane into the acid build up compartment; 
 a second cation exchange membrane interposed between the acid build up compartment and the anode compartment, the second cation exchange membrane being configured to exchange ions received from the anode compartment to an opposed surface of the second cation exchange membrane into the acid build up compartment; 
 an inlet through which the salt-containing solution is received into the salt depletion compartment; 
 a gas inlet positioned in the cathode compartment through which the gas comprising O 2  is introduced into contact with the gas diffusion electrode; and 
 at least one outlet through which a product is removed from an interior of the membrane electrolysis cell. 
 
     
     
       15. The membrane electrolysis cell of  claim 14 , wherein the catalyst layer is hydrophobic or hydrophilic. 
     
     
       16. The membrane electrolysis cell of  claim 14 , wherein the catalyst layer comprises a catalyst and an anion exchange ionomer. 
     
     
       17. The membrane electrolysis cell of  claim 16 , wherein the catalyst comprises a transition metal. 
     
     
       18. The membrane electrolysis cell of  claim 16 , wherein the catalyst comprises Pt. 
     
     
       19. The membrane electrolysis cell of  claim 16 , wherein the anion exchange ionomer comprises Fumion™ ionomer or Ionomr™ anion exchange ionomer. 
     
     
       20. The membrane electrolysis cell of  claim 14 , wherein the diffusion layer comprises carbon fiber paper, carbon felt, carbon cloth, or a porous metal structure.